1. Field of the Invention
The present invention relates to an information signal processing apparatus which records/plays-back information signals consisting of image and audio signals onto/of a recording medium such as DVD, etc. and, more particularly, a video disk recorder, etc. which are able to compress video information at a predetermined rate based on a compression variable conversion rate system such as MPEG (Moving Picture Experts Group) to record them, and play back the recorded signals.
2. Description of the Prior Art
In recent years, there are information signal processing (recording/playing) apparatuses such as a DVD system, which can compress the information signals such as the television signals via the MPEG compression variable conversion rate system, for example, to record them, and then play back the recorded signals. The DVD system records the information signals on the optical disk, which has a diameter of 12 cm and a recording capacity of 4.7 GB, via the variable rate system. Since such DVD system enables a large capacity recording and is excellent in so-called random access property, it has such an advantage that such DVD system can record/play back quickly a desired location of the recording region.
Then, normally the information signal processing (recording/ playing) apparatus of this type has a mode of playing back the ROM DVD optical disk on which particular information have been recorded in advance. However, a mode of recording the information signal such as the television signal in real time is now researched and developed actively.
FIG. 1 is a block diagram showing schematically a video disk recorder 700 having the compression variable conversion rate system in the prior art. As shown in FIG. 1, in this video disk recorder 700, the externally input video signal is compressed by a variable-rate encoder 701, and then recorded on a recordable disk 703 via a recording/playing circuit 702. Meanwhile, a control circuit 603 controls the variable-rate encoder 701 and the recording/playing circuit 702 according to a level of the recording picture quality and the recording time which are instructed by the user.
In the video disk recorder 700 in the prior art, the control circuit 603 changes a compression rate of the image, which is given by the variable-rate encoder 701, depending upon complexity of the contents of the input images and quickness of the motion of the subject to thus enable large-capacity and high quality picture recording. In more detail, the control circuit 603 increases the compression rate to lower the bit rate of the signals which are sent out to the recording/playing circuit 702 if either the contents of the video signal is monotonous or the motion of the subject is small, while the control circuit 603 decreases the compression rate to enhance the bit rate if either the image on the screen is complicated or the subject moves quickly.
However, if so-called real time coding recording by which the program portion of the TV program is recorded in real time, for example, is effected by using the above video disk recorder 700 in the prior art, it is difficult to forecast the succeeding development of the program contents. Therefore, there is such a problem that a remaining capacity of the optical disk 703 and the compression rate of the image cannot be properly balanced. For example, as shown in FIG. 2, when a 60-minute program is now recorded, the program has been recorded for 50 minutes after the start of the program while compressing the program at the average bit rate of 4 Mbps, nevertheless it is difficult to forecast the future development of the program contents at the time point of remaining 10 minutes.
More particularly, it is difficult to forecast whether to increase the bit rate like the case 1 in FIG. 2 since the program content reaches its climax within the remaining 10 minute and thus the image on the screen is complicated or the motion of the subject becomes quick, or to decrease the bit rate like the case 2 in FIG. 2 since the program content becomes quiet during the remaining 10 minute and thus the image becomes monotonous or the motion of the subject becomes slow.
Accordingly, it is impossible to decide the optimum compression rate by the real time coding recording. In order to compensate this, the technology for deciding a target coding amount of the succeeding screen based on the complexities of the past and current screens (Patent Application Publication (KOKAI) Hei 10-164577), and the technology for estimating the recordable remaining time (Patent Application Publication (KOKAI) Hei 10-172269) have been developed in the prior art.
However, these technologies decide the compression rate basically according to, the forecast. Therefore, if the forecast was wrong, the remaining capacity of the optical disk becomes small although the program has not yet ended. Thus, even if the program content reaches its climax and thus the image on the screen is complicated or the motion of the subject becomes quick, the DVD system cannot but increase the compression rate in order to lower the bit rate. As a result, there is a possibility that degradation of the picture quality is resulted in.
Meanwhile, upon recording, playing, and dubbing the television broadcasting, normally the commercial is the to-be-cut subject for most of the viewers. However, it is hard to discriminate between the program portion and the commercial portion of the TV program without fail. For this reason, the method of discriminating between the program portion and the commercial portion in view of the length of the soundless portion and the interval time between the soundless portions is disclosed in Patent Application Publication (KOKAI) Hei 8-235676, and the method of employing a plurality of detecting processes and then evaluating detected results based on the fuzzy logic is disclosed in Patent Application Publication (KOKAI) Hei 8-289244. Moreover, it has been widely known that the optical disk is excellent in the random access property.
The present invention has been made in view of the above circumstance in the prior art, and it is an object of the present invention to provide an information signal processing apparatus which can improve recording quality of a video signal on an optical disk by correlating an output of an information evaluating portion, which can weight information signals according to a degree of importance of the contents of the information signals, with a target value of a coding average rate, which is supplied to a variable-rate encoder.
It is another object of the present invention to provide an information signal processing apparatus which can overwrite new information signals on commercial portions, etc., which have a relatively low importance in program contents, with the use of a random access property of the optical disk, and can practically use the recording capacity at its maximum by utilizing effectively recording regions of a recording medium such as DVD, etc. to thus enable the high picture quality video recording.
It is still another object of the present invention to provide an information signal processing apparatus which can record a probability of being program (or commercial) evaluated in recording in a memory or on the recording medium and then employ the probability to control a player at the time of play back.
In order to achieve the above objects, there is provided an information signal processing apparatus comprising: an information evaluating portion for weighting individually information signals which are input sequentially according to contents of the information signals; a controlling portion for generating compression rates for respective information signals according to corresponding weights and outputting the compression rates; a compressing portion for compressing input information signals based on the corresponding compression rates generated by the controlling portion; and a recording portion for recording the information signals which are compressed by the compressing portion on a recording medium.
In the preferred embodiment of the present invention, the information evaluating portion weights heavily the information signals according to a higher degree of importance of the contents of the information signals respectively, and the controlling portion generates lower compression rates according to heaviness of the weights respectively.
In the preferred embodiment of the present invention, the information signals are television signals, the information evaluating portion weights more heavily the television signals according to height of probability of not being commercial respectively, and the controlling portion generates lower compression rates according to heaviness of weights respectively.
According to the above configuration of the present invention, the compression rate of the unimportant portion such as the commercial can be increased to reduce an amount of information when such unimportant portion is recorded on the recording medium, while the compression rate of the important portion of the television signals such as the program can be decreased when such important portion is recorded on the recording medium. Therefore, the capacity of the recording medium can be effectively utilized while achieving improvement of the picture quality.
The preferred embodiment of the present invention further comprises a storing portion for storing sequentially the weights to correspond to the information signals respectively, wherein the controlling portion controls the recording portion to overwrite new information signals on locations of the recording medium, in which the information signals have already been recorded, based on the weights stored in the storing portion.
The preferred embodiment of the present invention further comprises a storing portion for storing sequentially the weights to correspond to the information signals respectively, wherein the controlling portion controls the recording portion to overwrite new information signals on locations of the recording medium, in which the information signals have already been recorded, in an order of lower corresponding weights stored in the storing portion.
The preferred embodiment of the present invention further comprises a storing portion for storing sequentially the weights to correspond to the television signals respectively, wherein the controlling portion controls the recording portion to overwrite new television signals on locations of the recording medium, in which the television signals have already been recorded, in an order of lower corresponding weights stored in the storing portion.
According to the above configuration of the present invention, since the important information signal can be overwritten on the regions in which the unimportant information signal has already been recorded when the capacity of the recording medium lacks during recording the signals on the recording medium in real time, the remaining important information signal can be recorded without degradation of the picture quality. At that time, in the case of the television signal, for example, the information signal is overwritten on the regions which has a high possibility that the commercial is recorded therein. Accordingly, the capacity of the recording medium can be utilized more effectively. If the recording medium consists of the optical disk which has a random access property, the television signal can be played back smoothly when such television signal is recorded discontinuously.
The preferred embodiment of the present invention further comprises a sound volume detecting portion for detecting sound volume of audio signals included in the television signals; and a soundless portion detecting portion for detecting a soundless portion of the audio signals, wherein the information evaluating portion estimates a probability of not being commercial of the television signals based on results detected by the sound volume, detecting portion and the soundless portion detecting portion.
The preferred embodiment of the present invention further comprises a frame information analyzing portion for analyzing frame information of the video signals included in the television signals; and a luminance distribution analyzing portion for analyzing luminance distribution of the video signals, wherein the information evaluating portion estimates a probability of not being commercial of the television signals based on results analyzed by the frame information analyzing portion and the luminance distribution analyzing portion.
The preferred embodiment of the present invention further comprises a storing portion for storing sequentially the weights to correspond to the information signals respectively; and a playing portion for playing back the information signals which are recorded on the recording medium at a variable speed in accordance with corresponding weights stored in the storing portion.
The preferred embodiment of the present invention further comprises a storing portion for storing sequentially the weights to correspond to the television signals respectively; and a playing portion for playing back the television signals which are recorded on the recording medium at a variable speed in accordance with corresponding weights stored in the storing portion.
According to the above configuration of the present invention, the important portion of the television signals such as the program can be played back at a low speed, whereas the unimportant portion such as the commercial can be played back at a high speed. Therefore, the information signal can be played back effectively.